Optical modulator and system having tunable image enhancement

Abstract

An optical modulator (19) utilizes a variable beam splitter arrangement having two separate plano-periodic cylindrical lens arrays (20 and 22) arranged as a sandwiched air-spaced assembly with the plano surfaces facing outwardly from the assembly. The assembly further includes a means (26) for controllably translating or moving one of the lenses relative to the other. The periodic array is formed as alternating concave and convex cylindrical structures. In a nominal setting, the optical axes of the concave structures of one of the lens arrays are aligned with the optical axes of the convex structures of the other so that the assembly acts as an afocal window having little impact when placed in an optical system. To adjust the beam splitting properties, one lens array is slightly translated with respect to the other to cause controlled misalignment of the two lens array surfaces. The present invention is particularly suited for tuning the point spread function of an electronic imaging system.

I claim: 
     
       1. A method for adjusting a point spread function of an imaging system comprising the steps of: positioning an optical modulator along an optical axis of said imaging system, said optical modulator comprising a first and second optical element each having a lens array comprising alternating convex and concave light modifying structures formed on a surface thereof; and   translating the orientation of the second optical element relative to the first optical element so as to controllably split any light passing through said modulator to create a modified point spread function for said imaging system.   
     
     
       2. The method of claim 1 wherein said translating step comprises tuning the point spread function by selectively adjusting the amount of translation. 
     
     
       3. The method of claim 2 wherein said translating step further comprises adjusting the amount of translation by manually adjusting a set screw. 
     
     
       4. In an imaging system, an optical modulator for modifying a point spread function of an optically formed image comprises: a modulator assembly positioned along an optical axis of said imaging system comprising a first and second optical element each having at least a first lens array comprising alternating convex and concave light modifying structures formed on a surface thereof, wherein said light modifying structures are oriented relative to each other so as to split any incident light beam passing through said modulator assembly to create a desired point spread function.   
     
     
       5. The modulator of claim 4 further comprising means connected to said second optical element for selectively translating said second element relative to said first element so as to tune the point spread function. 
     
     
       6. The modulator of claim 5 wherein said means for selectively translating said second modulator element comprises a set screw. 
     
     
       7. The modulator of claim 4 wherein the alternating convex and concave light modifying structures of said first element and said second element each comprise a cylindrical structure having radii of identical magnitude. 
     
     
       8. The modulator of claim 4 wherein the alternating convex and concave light modifying structures of said first element and said second element are formed by utilizing gradients of index of refraction. 
     
     
       9. The modulator of claim 4 wherein the alternating convex and concave light modifying structures of said first element and said second element are formed by utilizing a holographic material. 
     
     
       10. The modulator of claim 4 further comprising a means connected for moving said second element to change an angle relative to the surface of said first element. 
     
     
       11. The modulator of claim 4 wherein said first optical element comprises a second lens array comprising alternating convex and concave light modifying structures formed on a second outer surface opposite the first lens array, and wherein said modulator further comprises a third optical element having a lens array comprising alternating convex and concave light modifying structures formed on an outer surface thereof, wherein said first and third optical element are positioned so that said second lens array of said first element and the lens array of said third element oppose each other, and said light modifying structures are oriented relative to each other so as to split any incident light beam passing through said modulator assembly in a different orientation from said first and second elements to create a desired point spread function in two axes. 
     
     
       12. The modulator of claim 11 further comprising a means connected to said third optical element for selectively translating said third element relative to said first element so as to tune the point spread function. 
     
     
       13. The modulator of claim 12 wherein said means for selectively translating said third element comprises a second set screw. 
     
     
       14. The modulator of claim 11 further comprising a means connected to at least said first or second element for moving said element to change an angle relative to the surface of said third element.